1. Field of the Invention
The present invention relates to a circumferential flow pump which is accommodated in a fuel tank of a vehicle to press-feed fuel to an internal combustion engine, for example.
2. Description of the Related Art
A conventional circumferential flow pump is designed so that the groove cross-section area of an annular feed passage disposed in a pump cover and the groove cross-section area of an annular feed passage disposed in a pump base are set to be substantially equal to each other, and the dimension of a space formed in a vane wheel so as to confront the feed passage of the pump cover and the dimension of a space formed in the vane wheel so as to confront the feed passage-of the pump base are set to be substantially equal to each other, whereby the pressure balance in a pump chamber formed by the pump cover, the pump base and the vane wheel is made uniform as disclosed in Japanese Patent No. 2,962,828 (Patent Document 1).
In the conventional circumferential flow pump thus constructed, when fuel press-fed from the circumferential flow pump to the internal combustion engine is reduced, the pressure in the neighborhood of a discharge port of the pump base is increased and force acts on the vane wheel so that the vane wheel is pressed against the pump cover side. Therefore, the vane wheel is inclined and thus rotated while coming into contact with the pump cover or the pump base, so that the sliding resistance thereof is increased and the operating current of an electrically-driven motor for rotating the vane wheel is increased. In addition, the discharge amount is reduced, and the fuel press-fed from the circumferential flow pump to the internal combustion engine is reduced.